1. Field of the Invention
The field of the invention relates to a hospital bed including a mechanism for adjusting the height thereof and a safety system for controlling the operation of said mechanism.
2. Brief Description of the Prior Art
Hospital beds are designed to quickly and smoothly assume a full range of medical positions. Electric motors have been employed to operate head, knee and height functions. One such bed utilizes three direct drive 0.1 horsepower motors, one for each of these three functions. Pneumatic patient controls mounted on a safety rail allow the bed to be adjusted to nearly any desired position. Lock out switches may be provided out of the patient's reach at the foot end of the bed when restricted positioning is required.
A hosptial bed is raised or lowered by causing the mattress-supporting frame to move with respect to a stationary frame positioned below. Since it may take about thirty seconds to move between the highest and lowest positions, many beds have been equipped with "constant-on" switches to allow the nurse to simply press a button to effect full raising or lowering. This allows the nurse to perform other duties as the bed is moving toward the desired position.
A significant disadvantage of the "constant-on" feature is that it may result in injury if accidentally actuated while a person is under the bed. This may occur in children's wards where they may climb out of a bed and so position themselves. It can also be a problem where a patient has a psychological disorder. Since a pair of bed frames are moving constantly closer to one another when the bed is lowered, any part of the body trapped therebetween can be subject to serious injury.
One solution has been to avoid the use of a constant-on switch. While effective, it does require the nurse to keep her finger on the button for a period of time and restricts her from proceding with other tasks.